Revamp signatures and break header caching on FF

Signatures, instead of consisting of the secure salt followed by the unique
value generated from the URL, are now the unique value generated from the
policy value (which will follow them) succeeded by the URL.

CSP headers are now _always_ cleared on FF, regardless of whether the page
is whitelisted or not. This means whitelisting takes effect on page reload,
rather than only when caching occurs. However, it obviously presents security
issues; refinment will occur in a future commit.

1 files changed, 13 insertions, 16 deletions

diff --git a/background/policy_injector.js b/background/policy_injector.js
index 9e8ed61..8a767fb 100644
--- a/background/policy_injector.js
+++ b/background/policy_injector.js
@@ -12,6 +12,7 @@
  * IMPORT get_storage
  * IMPORT browser
  * IMPORT is_chrome
+ * IMPORT is_mozilla
  * IMPORT gen_unique
  * IMPORT gen_nonce
  * IMPORT url_item
@@ -45,23 +46,24 @@ function is_our_header(header, rule)
 function url_inject(details)
 {
     const targets = url_extract_policy(details.url);
-    if (targets.policy) {
+    if (targets.valid_sig) {
 	return;
-    } else if (targets.signed) {
+    } else if (targets.policy) {
 	/* Redirect; update policy */
 	targets.target = targets.target2;
 	delete targets.target2
     }
 
-    let redirect_url = targets.base_url + targets.sig;
     let [pattern, settings] = query_best(targets.base_url);
     if (!pattern)
 	/* Defaults */
 	settings = {};
     
     const policy = {allow: settings.allow, nonce: gen_nonce()};
+    const policy_string = encodeURIComponent(JSON.stringify(policy));
+    const sig = gen_unique(policy_string + targets.base_url);
     
-    redirect_url += encodeURIComponent(JSON.stringify(policy));
+    let redirect_url = targets.base_url + '#' + sig + policy_string;
     if (targets.target)
 	redirect_url += targets.target;
     if (targets.target2)
@@ -73,31 +75,26 @@ function url_inject(details)
 function inject(details)
 {
     const targets = url_extract_policy(details.url);
-    if (!targets.policy)
+    if (!targets.valid_sig)
 	/* Block unsigned requests */
 	return {cancel: true};
 
     const rule = csp_rule(targets.policy.nonce);
 
-    var headers;
+    var headers = details.responseHeaders;
 
-    if (targets.policy.allow) {
+    if (!targets.policy.allow || is_mozilla)
 	/*
-	 * Chrome doesn't have the buggy behavior of repeatedly injecting a
-	 * header we injected once. Firefox does and we have to remove it there.
+	 * Chrome doesn't have the buggy behavior of caching headers
+	 * we injected. Firefox does and we have to remove it there.
 	 */
-	if (is_chrome)
-	    return {cancel: false};
-
-	headers = details.responseHeaders.filter(h => !is_our_header(h, rule));
-    } else {
-	headers = details.responseHeaders.filter(h => !is_csp_header(h));
+	headers = headers.filter(h => !is_csp_header(h));
 
+    if (!targets.policy.allow)
 	headers.push({
 	    name : header_name,
 	    value : rule
 	});
-    }
 
     return {responseHeaders: headers};
 }